from bench to battlefield: the neuroscience of combat stress risk and resilience deane aikins paul...
TRANSCRIPT
From Bench to Battlefield:The Neuroscience of Combat
Stress Risk and Resilience
Deane Aikins Paul Morrissey National Center for PTSD United States Army
Yale School of Medicine
Objectives
• Describe how neuroscience research methods help us better define combat stress– Risk– Resilience
• Translate neuroscience research methods into clinical practice/ operations.
What is “normal” stress response?
• OIF/OEF PTSD risk is 1 in 5.
• A monozygotic twin makes risk 1 in 3.
• Civilian research focused on illness risk
• We need to better understand: – Resistance: same stress exposure, no illness – Resilience: faster recovery from illness
• What can neurobiology of fear tell us?
Biobehavioral model of fear
• PTSD thought of in terms of Pavlovian conditioning:– An over-reaction to threat cue.– This model used to develop new drug trials.– Yet, only one of six PTSD studies support this model.– Why so much variance in PTSD fear learning ability?
Neurobiology of Fear
• Conditioned fear ability associated with amygdala brain region
• Amygdala activity regulated in part by serotonin neurotransmitter.
• Serotonin affects depression and anxiety.
Serotonin TransporterPromoter Variant (5-HTTLPR)
• Common polymorphism in promoter region regulates gene expression
• Genotypes: l/l or l/s or s/s
• Long variant = increased serotonin “RESILIENCE”
• Short variant = reduced serotonin “RISK”
genome locus gene site
Pair of Chromosomes(2 Strands of DNA each)
Current Study
• Investigate ability to learn fear and safety cues
• Compare PTSD and Stress Resistant Service Members
• Study brain activity during fear learning
• Categorize Service Members by Serotonin risk and resilience gene variants.
Participants
• 10th Mountain Division (LI).– Right handed, medication-free, metal-free.
• Active Duty Male Service Members:– PTSD (n=14).– Combat Resilient (n=14).– Pre-Deployed (n=15).
Research Procedure
DemographicsPTSD Stress
Resistant
Age 24 (3) 24 (3)
Education 12 (1) 13 (1)
Yrs. Service 4 (3) 5 (2)
CES 30 (7) 27 (6)
CAPS 66 (4) 16 (4)
Identifying Threat (CS+) from Safety (CS-)
Trials 1-5 Trials 1-5 0
0.2
0.4
0.6 Combat Resilient PTSD
CS+
CS-
0
0.2
0.4
0.6
Pre-deployed Combat Resilient PTSD
CS+
CS-
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
ss(risk)
sl/ls ll(resil)
ss(risk)
sl/ls ll(resil)
CS+CS-
PTSD Stress Resistant
The ability to discriminate threat from safetyvaries by 5HT2C polymorphism
uAm
p
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
ss(risk)
sl/ls ll(resil)
ss(risk)
sl/ls ll(resil)
CS+CS-
PTSD Stress Resistant
The ability to discriminate threat from safetyvaries by 5HT2C polymorphism
uAm
p
Combat Stress 28 30 28 26 28 30
PTSD severity 64 74 56 5 22 6
fMRI Results: Stress Resistant
Stress Resistant Service Membersshow greater CR+ in Lateral BA6.
BA6 is defined as a pre-motorarea, often found active duringcognitive tasks to prepare foraction.
Activity motor areas may inhibitactivity in fear network.
Summary: PTSD
• No support for “over reaction” model.– Over time, a “general alarm”
• “Risk” gene associated increased PTSD severity and poor ability to identify threat from safety signals.
Summary: Stress Resistance
• Stress Resistant Service Members not “fearless”.
• Make good use of threat and safety cues.– Conditioned fear response engages brain areas
for motor output planning.– Likely prevents fear circuit from over-reacting.
• Provide building blocks for operational functioning.
Translation to Clinical Value
• In separate pilot study:– Veterans with strong conditioned response responded
very well to 8 wk SNRI treatment (Duloxetine).
– Veterans with weak/no conditioned response saw no improvement.
• Conditioned Fear provides marker for treatment.• Need to change models for treatment.• Can we screen for stress resistant Service
Members?
Research Team• Yale/ National Center for PTSD
– Joel Gelernter– John Krystal– Steven Southwick
• 10th Mountain Division (LI)– LTC Paul Morrissey– Todd Benham
• MIT– Susan Whitfield-Gabrieli
• NYU– Joe LeDoux
• Institute of Living– Hank Schwartz– Godfrey Pearlson– Robert Astur – Kent Kiehl
